// Copyright 2013 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_WEBSOCKETS_WEBSOCKET_DEFLATE_PREDICTOR_H_
#define NET_WEBSOCKETS_WEBSOCKET_DEFLATE_PREDICTOR_H_

#include <stddef.h>

#include <memory>
#include <vector>

#include "net/base/net_export.h"

namespace net {

struct WebSocketFrame;

// WebSocketDeflatePredictor is an interface class used for judging whether
// a WebSocketDeflateStream should compress a message or not.
class NET_EXPORT_PRIVATE WebSocketDeflatePredictor {
public:
    enum Result {
        // Deflate and send the message.
        DEFLATE,
        // Do not deflate and send the original message.
        DO_NOT_DEFLATE,
        // Try compressing the message and send the smaller one of the original
        // and the compressed message.
        // Returning this result implies that the deflater is running on
        // DoNotTakeOverContext mode and the entire message is visible.
        TRY_DEFLATE,
    };

    virtual ~WebSocketDeflatePredictor() { }

    // Predicts and returns whether the deflater should deflate the message
    // which begins with |frames[frame_index]| or not.
    // |frames[(frame_index + 1):]| consists of future frames if any.
    // |frames[frame_index]| must be the first frame of a data message,
    // but future frames may contain control message frames.
    // |frames[frame_index]| cannot be recorded yet and all preceding
    // data frames have to be already recorded when this method is called.
    virtual Result Predict(
        const std::vector<std::unique_ptr<WebSocketFrame>>& frames,
        size_t frame_index)
        = 0;

    // Records frame data for future prediction.
    // Only data frames should be recorded. Do not pass control frames' data.
    // All input data frames for the stream must be recorded in order.
    virtual void RecordInputDataFrame(const WebSocketFrame* frame) = 0;

    // Records frame data for future prediction.
    // Only data frames should be recorded. Do not pass control frames' data.
    // All data frames written by the stream must be recorded in order
    // regardless of whether they are compressed or not.
    virtual void RecordWrittenDataFrame(const WebSocketFrame* frame) = 0;
};

} // namespace net

#endif // NET_WEBSOCKETS_WEBSOCKET_DEFLATE_PREDICTOR_H_
